feat(postgres): Introduce chained error variants
Introduces error variants for external crate errors and internal errors. Additional context can be provided at sites where errors occur using a simple `.context()` call.
This commit is contained in:
Vincent Ambo
parent
43f71ae82f
commit
68060fea13
2 changed files with 91 additions and 33 deletions
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@ -2,8 +2,68 @@
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//! occur while dealing with persisted state machines.
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use std::result;
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use std::fmt::Display;
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use uuid::Uuid;
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// errors to chain:
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use serde_json::Error as JsonError;
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use postgres::Error as PgError;
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pub type Result<T> = result::Result<T, Error>;
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#[derive(Debug)]
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pub enum Error { SomeError }
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pub struct Error {
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pub kind: ErrorKind,
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pub context: Option<String>,
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}
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#[derive(Debug)]
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pub enum ErrorKind {
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/// Errors occuring during JSON serialization of FSM types.
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Serialization(String),
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/// Errors occuring during communication with the database.
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Database(String),
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/// State machine could not be found.
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FSMNotFound(Uuid),
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/// Action could not be found.
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ActionNotFound(Uuid),
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}
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impl <E: Into<ErrorKind>> From<E> for Error {
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fn from(err: E) -> Error {
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Error {
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kind: err.into(),
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context: None,
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}
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}
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}
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impl From<JsonError> for ErrorKind {
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fn from(err: JsonError) -> ErrorKind {
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ErrorKind::Serialization(err.to_string())
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}
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}
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impl From<PgError> for ErrorKind {
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fn from(err: PgError) -> ErrorKind {
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ErrorKind::Database(err.to_string())
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}
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}
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/// Helper trait that makes it possible to supply contextual
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/// information with an error.
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pub trait ResultExt<T> {
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fn context<C: Display>(self, ctx: C) -> Result<T>;
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}
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impl <T, E: Into<Error>> ResultExt<T> for result::Result<T, E> {
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fn context<C: Display>(self, ctx: C) -> Result<T> {
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self.map_err(|err| Error {
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context: Some(format!("{}", ctx)),
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.. err.into()
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})
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}
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}
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@ -17,8 +17,9 @@ extern crate uuid;
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#[cfg(test)] extern crate finito_door;
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mod error;
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pub use error::{Result, Error};
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pub use error::{Result, Error, ErrorKind};
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use error::ResultExt;
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use chrono::prelude::{DateTime, Utc};
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use finito::{FSM, FSMBackend};
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use postgres::{Connection, GenericConnection};
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@ -118,9 +119,9 @@ impl <State: 'static> FSMBackend<State> for FinitoPostgres<State> {
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let id = Uuid::new_v4();
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let fsm = S::FSM_NAME.to_string();
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let state = serde_json::to_value(initial).expect("TODO");
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let state = serde_json::to_value(initial).context("failed to serialise FSM")?;
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self.conn.execute(query, &[&id, &fsm, &state]).expect("TODO");
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self.conn.execute(query, &[&id, &fsm, &state]).context("failed to insert FSM")?;
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return Ok(id);
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@ -146,7 +147,7 @@ impl <State: 'static> FSMBackend<State> for FinitoPostgres<State> {
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S::State: From<&'a State>,
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S::Event: Serialize + DeserializeOwned,
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S::Action: Serialize + DeserializeOwned {
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let tx = self.conn.transaction().expect("TODO");
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let tx = self.conn.transaction().context("could not begin transaction")?;
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let state = get_machine_internal(&tx, key, true)?;
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// Advancing the FSM consumes the event, so it is persisted first:
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@ -163,8 +164,8 @@ impl <State: 'static> FSMBackend<State> for FinitoPostgres<State> {
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}
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// And finally the state is updated:
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update_state(&tx, key, &new_state).expect("TODO");
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tx.commit().expect("TODO");
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update_state(&tx, key, &new_state)?;
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tx.commit().context("could not commit transaction")?;
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self.run_actions::<S>(key, action_ids);
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@ -211,9 +212,9 @@ pub fn insert_machine<C, S>(conn: &C, initial: S) -> Result<Uuid> where
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let id = Uuid::new_v4();
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let fsm = S::FSM_NAME.to_string();
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let state = serde_json::to_value(initial).expect("TODO");
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let state = serde_json::to_value(initial).context("failed to serialize FSM")?;
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conn.execute(query, &[&id, &fsm, &state]).expect("TODO");
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conn.execute(query, &[&id, &fsm, &state])?;
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return Ok(id);
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}
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@ -233,9 +234,10 @@ where
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let id = Uuid::new_v4();
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let fsm = S::FSM_NAME.to_string();
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let event_value = serde_json::to_value(event).expect("TODO");
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let event_value = serde_json::to_value(event)
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.context("failed to serialize event")?;
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conn.execute(query, &[&id, &fsm, &fsm_id, &event_value]).expect("TODO");
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conn.execute(query, &[&id, &fsm, &fsm_id, &event_value])?;
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return Ok(id)
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}
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@ -254,12 +256,13 @@ fn insert_action<C, S>(conn: &C,
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let id = Uuid::new_v4();
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let fsm = S::FSM_NAME.to_string();
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let action_value = serde_json::to_value(action).expect("TODO");
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let action_value = serde_json::to_value(action)
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.context("failed to serialize action")?;
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conn.execute(
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query,
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&[&id, &fsm, &fsm_id, &event_id, &action_value, &ActionStatus::Pending]
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).expect("TODO");
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)?;
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return Ok(id)
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}
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@ -274,13 +277,11 @@ fn update_state<C, S>(conn: &C,
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UPDATE machines SET state = $1 WHERE id = $2
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"#;
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let state_value = serde_json::to_value(state).expect("TODO");
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let res_count = conn.execute(query, &[&state_value, &fsm_id])
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.expect("TODO");
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let state_value = serde_json::to_value(state).context("failed to serialize FSM")?;
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let res_count = conn.execute(query, &[&state_value, &fsm_id])?;
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if res_count != 1 {
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// TODO: not found error!
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unimplemented!()
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Err(ErrorKind::FSMNotFound(fsm_id).into())
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} else {
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Ok(())
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}
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@ -307,13 +308,12 @@ fn get_machine_internal<C, S>(conn: &C,
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SELECT state FROM machines WHERE id = $1
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"#);
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let rows = conn.query(&query, &[&id]).expect("TODO");
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let rows = conn.query(&query, &[&id]).context("failed to retrieve FSM")?;
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if let Some(row) = rows.into_iter().next() {
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Ok(serde_json::from_value(row.get(0)).expect("TODO"))
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Ok(serde_json::from_value(row.get(0)).context("failed to deserialize FSM")?)
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} else {
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// TODO: return appropriate not found error
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Err(Error::SomeError)
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Err(ErrorKind::FSMNotFound(id).into())
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}
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}
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@ -328,14 +328,14 @@ fn get_action<C, S>(conn: &C, id: Uuid) -> Result<(ActionStatus, S::Action)> whe
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WHERE id = $1 AND fsm = $2
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"#);
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let rows = conn.query(&query, &[&id, &S::FSM_NAME]).expect("TODO");
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let rows = conn.query(&query, &[&id, &S::FSM_NAME])?;
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if let Some(row) = rows.into_iter().next() {
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let action = serde_json::from_value(row.get(1)).expect("TODO");
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let action = serde_json::from_value(row.get(1))
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.context("failed to deserialize FSM action")?;
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Ok((row.get(0), action))
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} else {
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// TODO: return appropriate not found error
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Err(Error::SomeError)
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Err(ErrorKind::ActionNotFound(id).into())
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}
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}
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@ -352,15 +352,13 @@ fn update_action_status<C, S>(conn: &C,
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WHERE id = $3 AND fsm = $4
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"#;
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let result = conn.execute(&query, &[&status, &error, &id, &S::FSM_NAME])
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.expect("TODO");
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let result = conn.execute(&query, &[&status, &error, &id, &S::FSM_NAME])?;
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if result != 1 {
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// TODO: Fail in the most gruesome way!
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unimplemented!()
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Err(ErrorKind::ActionNotFound(id).into())
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} else {
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Ok(())
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}
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Ok(())
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}
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/// Execute a single action in case it is pending or retryable. Holds
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@ -408,6 +406,6 @@ fn run_action<S>(tx: Transaction, id: Uuid, state: &S::State, _fsm: PhantomData<
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},
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};
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tx.commit().expect("TODO");
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tx.commit().context("failed to commit transaction")?;
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Ok(result)
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}
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